Fixed bugs with explicit abort (XABORT)

The explicit abort (XABORT) was not working properly. First, on issue
the ReorderBufferEntry::issue() was continued after flushing the pipeline
on XABORT, which caused erroneous behaviour. Second, in
TsxCache::handle_upper_interconnect() the check_tsx_invalidated()
function is called on XABORT, but it does not make sense, since it mixes
the TsxStatus and TsxMESICacheLineState data types up.
Fixed bug with XTEST implementation

The result of the XTEST instruction was wrong. According to the
specification the ZF flag needs to be cleared, if the XTEST instruction
is executed in a transaction. Otherwise the ZF flag is to be set.